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Chitosan is a polysaccharide resulting from chitin deacetylation. It has demonstrated interesting characteristics in the field of adhesion but loses most of its adhesive resistance in moist environment. A chemical crosslinking of chitosan with genipin has been implemented to improve its adhesive properties in the presence of water. The study of crosslinking kinetics using rheology revealed its dependency on crosslinking rate and chitosan concentration. The capacity of the chitosan-genipin systems for water absorption has been quantified as their Free Swelling Capacity. The cross-linkage of chitosan by genipin (1% w/w) decreased significantly its ability for water absorption. Finally, the adhesive strength of several chitosans be they supplemented or not with genipin and/or glycerol used as plasticizer have been performed on Thick Adherent Shear Test samples of beech wood according to standard EN 204:2016 and EN 205:2016. The chitosan adhesive formulation containing genipin and glycerol exhibits the better adhesive properties on wood and presents higher water resistance compared to the native chitosan formulation. [ABSTRACT FROM AUTHOR]

Here, we report work on developing an enzymatic process to improve the functionalities of industrial lignin. A kraft lignin sample prepared from marine pine was treated with the high-redox-potential laccase from the basidiomycete fungus Pycnoporus cinnabarinus at three different concentrations and pH conditions, and with and without the chemical mediator 1-hydroxybenzotriazole (HBT). Laccase activity was tested in the presence and absence of kraft lignin. The optimum pH of PciLac was initially 4.0 in the presence and absence of lignin, but at incubation times over 6 h, higher activities were found at pH 4.5 in the presence of lignin. Structural changes in lignin were investigated by Fourier-transform infrared spectroscopy (FTIR) with differential scanning calorimetry (DSC), and solvent-extractable fractions were analyzed using high-performance size-exclusion chromatography (HPSEC) and gas chromatography–mass spectrometry (GC–MS). The FTIR spectral data were analyzed with two successive multivariate series using principal component analysis (PCA) and ANOVA statistical analysis to identify the best conditions for the largest range of chemical modifications. DSC combined with modulated DSC (MDSC) revealed that the greatest effect on glass transition temperature (Tg) was obtained at 130 U g cm−1 and pH 4.5, with the laccase alone or combined with HBT. HPSEC data suggested that the laccase treatments led to concomitant phenomena of oligomerization and depolymerization, and GC–MS revealed that the reactivity of the extractable phenolic monomers depended on the conditions tested. This study demonstrates that P. cinnabarinus laccase can be used to modify marine pine kraft lignin, and that the set of analytical methods implemented here provides a valuable tool for screening enzymatic treatment conditions. [ABSTRACT FROM AUTHOR]

Foaming process can be monitored under batch or continuous flows conditions. In the batch process, foaming is time-dependent and the foaming efficiency is controlled by the operator. On the other hand, in the continuous process, the foaming efficiency is only monitored by gas and liquid flow rates. The aim of this work is to compare the two technologies to perform porous scaffold biomaterial based on chitosan (a biocompatible polysaccharide) as well as calcium (Ca2+) and silica (SiO2) (two osteogenesis compounds). Diverse recipes using chitosan (CS) solution (2% (w/v)) in acetic acid (1% (v/v in distilled water)) mixed with whey protein isolate (WPI) (2% (w/v)) as natural surfactant were studied. They were supplemented or not by hydroxyapatite powder (HAp) and tetraethyl orthosilicate (TEOS). A jacketed narrow annular gap unit (NAGU) was used to perform the continuous foaming process. For all experimentations, the mixture flow rate was maintained at 30 mL min-1. The influence of operating conditions such as gas and liquid flow rates was studied to obtain foams and final scaffold material with different densities and porosities. Some other recipes followed foaming under batch conditions. Generally, the recipes were placed in a vessel under mixing allowing the gas phase to come from the roof of the vessel. In this case, it becomes very difficult to control the density and the size distribution of bubbles in the final product. In both cases, liquid foams were analysed (density, bubble size distribution) and then freeze-dried for mechanical and porosity investigations using the dynamic mechanical analysis (DMA) system and scanning electron microscopy (SEM). It has been shown that the controlled injected gas affected the continuous phase, resulting in a lighter and higher porous structure, a more homogeneous appearance, and a more uniform distribution of osteogenesis components compared to one obtained using batch operation. The obtained porous materials exhibited good properties (porosity, interconnectivity, and good HAp and silica distribution) and potential for future bone regeneration applications. [ABSTRACT FROM AUTHOR]

Today, chitosan (CS) is probably considered as a biofunctional polysaccharide with the most notable growth and potential for applications in various fields. The progress in chitin chemistry and the need to replace additives and non-natural polymers with functional natural-based polymers have opened many new opportunities for CS and its derivatives. Thanks to the specific reactive groups of CS and easy chemical modifications, a wide range of physico-chemical and biological properties can be obtained from this ubiquitous polysaccharide that is composed of β-(1,4)-2-acetamido-2-deoxy-d-glucose repeating units. This review is presented to share insights into multiple native/modified CSs and chitooligosaccharides (COS) associated with their functional properties. An overview will be given on bioadhesive applications, antimicrobial activities, adsorption, and chelation in the wine industry, as well as developments in medical fields or biodegradability. [ABSTRACT FROM AUTHOR]

One of the big global, environmental, and socioeconomic challenges of today is to make a transition from fossil fuels to biomass as a sustainable supply of renewable raw materials for industry. Growing public awareness of the negative environmental effects of petrochemical-based products adds to the need for alternative production chains, especially in materials science. One option lies in the value-added upcycling of agricultural byproducts, which are increasingly being used for biocomposite materials in transport and building sector applications. Here, sunflower by-product (obtained by grinding the stems) is considered as a source of natural fibers for engineered biocomposite material. Recent results are shown for the main mechanical properties of sunflower-based biocomposites and the socioeconomic impact of their use. This paper demonstrates that sunflower stem makes a good candidate feedstock for material applications. This is due not only to its physical and chemical properties, but also to its socioeconomic and environmental rationales. [ABSTRACT FROM AUTHOR]

ABSTRACT This study was conducted on the both solid and solubilized chitosans to propose an approach for the physico-chemical, thermal and mechanical characterizations of this polysaccharide. The polysaccharide used was a 90% deacetylated chitosan having a molecular weight of 98.4 kDa. The flow property of chitosan solutions was evaluated revealing a shear-thinning behavior. The thermal characterization was carried out by studying heat specific capacity, glass transition temperature, and thermal conductivity on chitosan dried specimens (solid state). Their Tg were measured by DSC and confirmed by DMA at 102 and 122°C depending on concentrations of initial chitosan solutions. The mechanical characterization was conducted by analyzing Young modulus, tensile strength, and elongation at break of chitosan specimens. They exhibited a higher elongation at break and a lower tensile strength when made from high concentrated chitosan solution (9% w/v). Differences in mechanical behavior of specimens were explained by differences of crystallinity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41257. [ABSTRACT FROM AUTHOR]

Highlights: [•] An insulating bio-based composite was made with chitosan and sunflower's stalks particles. [•] Its thermal, mechanical and acoustical properties were determined. [•] Its mechanical and thermal performances are competitive with those of other insulating bio-based materials. [ABSTRACT FROM AUTHOR]

Lignocellulosic by-products are frequently disposed by means of combustion. This study investigates an alternative route for corn cob and Kraft lignin resources in order to support circular economy. The respective plant-based fibres and filler were compounded for the first time together with a poly(lactic acid) (PLA) matrix. Consecutively, seven different biocomposites were processed by injection-moulding and further characterized. The biocomposite containing a mixture of Kraft lignin and corn cob (12 wt% in total) exhibited the highest flexural strength (84 MPa). A proper wetting of PLA onto the corn cob particles demonstrated a good compatibility at matrix/fibre interface. PLA molecular structure changed in presence of 20 wt% lignin filler, with effect on the glass transition temperature and on the composite mechanical strength. The fibres moderately influenced composites surface tension, while Kraft lignin contributed to a slight increase of surface hydrophobicity. Surface energy (σsTotal) of composites have been estimated at 27.6, 28.7 and 27.8 mN/m for PLA/KL-20, PLA/CC-10 and PLA/KL-15/CC-5 respectively. While the polar component (σsPolar) have been estimated at 17.8, 20.0 and 18.7 mN/m for PLA/KL-20, PLA/CC-10 and PLA/KL-15/CC-5 respectively. Unlike the PLA/corn cob composite, those containing Kraft lignin were entirely biodegraded within 2 months in industrial composting conditions study. The materials could be utilized for end-use products thanks to their good mechanical and thermal properties. By adding wood-lignin and corn by-products, materials cost and carbon footprint shall decrease in comparison to pure PLA, while being a biodegradable and sustainable replacement of polyolefins. [Display omitted] • Decreasing cost and carbon footprint of poly(lactic acid) (PLA) materials. • PLA was filled with corn cob by-products. • Conventional twin-screw extrusion and injection-moulding methods were employed. • Biocomposites properties were satisfying enough to apply them into end-products. • Kraft lignin-filled materials fully biodegraded in industrial compost within 60 days. [ABSTRACT FROM AUTHOR]

The potential of chitosan (CS) as wood adhesive was investigated in this study. The measurement of the bond strength of different CS-based formulations was carried out using double-lap shear tests. The best formulation tested was an adhesive composed of 6% of CS, 1% of glycerol, and 5 mmol/L of trisodium citrate dehydrate. Best bond strength from this formulation was found to be equal to 6.0 MPa in dried conditions and 1.6 MPa in wet conditions (specimens immersed for 3 h at 30°C in water). The failure in the double-lap joint tests mainly occurred in wood. Finally, the penetration of the rhodamine-labeled CS at 4% in the pinewood matrix was also studied using microtome and microscopy techniques to show interactions between CS-based adhesive and wood. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013 [ABSTRACT FROM AUTHOR]

Chitosan is a bio-sourced polysaccharide widely used in different fields from health to wastewater treatment through food supplements. Another important use of this polymer is adhesion. Indeed, the current demand to replace non-natural and hazardous polymers by greener ones is well present in the adhesive field and open good opportunities for chitosan and its derivatives. However, chitosan is water soluble and exhibits a poor water-resistance in the field of adhesion which reduces the possibilities of its utilization within the paste field. This review focuses on exploration of different ways available to modify the chitosan and transform it into a water-resistant adhesive. The first part concerns the chitosan itself and gives important information from the discovery of chitin to the pure chitosan ready to use. The second part reviews the background information relative to adhesion theories, ideal properties of adhesives and the characteristics of chitosan as an adhesive. The last part focuses on exploration of the possible modification of chitosan to make it a water-resistant chemical adhesive. [ABSTRACT FROM AUTHOR]

The present study was conducted to assess the impact of chitosan coating (1%) containing Artemisia fragrans essential oil (500, 1000, and 1500 ppm) as antioxidant and antimicrobial agent on the quality properties and shelf life of chicken fillets during refrigerated storage. After packaging meat samples, physicochemical, microbiological, and organoleptic attributes were evaluated at 0, 3, 6, 9, and 12 days at 4 °C. The results revealed that applied chitosan (CH) coating in combination with Artemisia fragrans essential oils (AFEOs) had no significant (p < 0.05) effects on proximate composition among treatments. The results showed that the incorporation of AFEOs into CH coating significantly reduced (p < 0.05) pH, thiobarbituric acid reactive substances (TBARS), and total volatile base nitrogen (TVB-N), especially for 1% CH coating + 1500 ppm AFEOs, with values at the end of storage of 5.58, 1.61, and 2.53, respectively. The coated samples also displayed higher phenolic compounds than those obtained by uncoated samples. Coated chicken meat had, significantly (p < 0.05), the highest inhibitory effects against microbial growth. The counts of TVC (total viable counts), coliforms, molds, and yeasts were significantly lower (p < 0.05) in 1% CH coating + 1500 ppm AFEOs fillets (5.32, 3.87, and 4.27 Log CFU/g, respectively) at day 12. Organoleptic attributes of coated samples also showed the highest overall acceptability scores than uncoated ones. Therefore, the incorporation of AFEOs into CH coating could be effectively used for improving stability and shelf life of chicken fillets during refrigerated storage. [ABSTRACT FROM AUTHOR]

A chemical modification by grafting alkyl chains using an octanal (C8) on chitosan was conducted with the aim to improve its water resistance for bonding applications. The chemical structure of the modified polymers was determined by NMR analyses revealing two alkylation degrees (10 and 15%). In this study, the flow properties of alkyl-chitosans were also evaluated. An increase in the viscosity was observed in alkyl-chitosan solutions compared with solutions of the same concentration based on native chitosan. Moreover, the evaluation of the adhesive strength (bond strength and shear stress) of both native and alkyl-chitosans was performed on two different double-lap adherends (aluminum and wood). Alkyl-chitosans (10 and 15%) maintain sufficient adhesive properties on wood and exhibit better water resistance compared to native chitosan. [ABSTRACT FROM AUTHOR]

Highlights • Bio-based composites with lignosulfonates and corn cob were developed. • High compaction pressure and low corn cob particle sizes improved Young modulus. • A rough surface of corn cob particles improved compressive properties of composites. • Adhesion between matrix and reinforcement occurred with interlocking action. Abstract Bio-based composites with lignosulfonates as a matrix and corn cob particles as reinforcement were developed. Their mechanical strength in compression mode was evaluated with determination of Young modulus (E) and ultimate compressive strength (σ max). The influence of fiber content, fibers particle size, and compaction pressure applied on the composite during processing was investigated with a design of experiments approach. The model enabled to calculate an optimum for σ max equal to 18 MPa for a corresponding Young modulus of 0.27 GPa. Particle size was found to be the most influent parameter on mechanical properties responses. In order to understand this dependency, an automated optical particle analysis was performed to measure size and shape of corn cob particles. Distribution leading to the highest σ max was the one with the less smooth surface of particles (low convexity shape parameter), providing a better mechanical adhesion between fiber and matrix. Increasing compaction pressure and fiber content was in favor of compressive strength. Interface between lignosulfonates and corn cob inside the composites was observed with X-ray microtomography technique. It was noticed that interlocking occurred between the two phases. [ABSTRACT FROM AUTHOR]